%-------------------------------------------------------------------------------
% SuiteSparse Matrix Collection, Tim Davis
% https://sparse.tamu.edu/Martin/marine1
% name: Martin/marine1
% [chemical oceanography; a marine nitrogen cycle inverse model]
% id: 2849
% date: 2018
% author: T. Martin, F. Primeau, K. L. Casciotti
% ed: T. Davis
% fields: name title A b id date author ed kind notes
% kind: chemical oceanography problem
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% notes:
% Martin/marine1: chemical oceanography; a marine nitrogen cycle inverse model   
%                                                                                
% A matrix submitted by Taylor Martin, Stanford, discussed the following paper:  
%                                                                                
% Title: Modeling oceanic nitrite concentrations and isotopes using a 3D         
% inverse N cycle model                                                          
% Authors: Taylor S. Martin(1), Francois Primeau(2), and Karen L. Casciotti(1)   
% (1) Stanford University, Department of Earth System Science                    
% (2) University of California, Irvine, Department of Earth System Science       
% Received: 05 Sep 2018                                                          
% Abstract. Nitrite (NO2-) is a key intermediate in the marine nitrogen (N) cycle
% and a substrate in nitrification, which produces nitrate (NO3-), as well as    
% water column N loss processes, denitrification and anammox. In models of the   
% marine N cycle, NO2- is often not considered as a separate state variable,     
% since NO3- occurs in much higher concentrations in the ocean. In oxygen        
% deficient zones (ODZs), however, NO2- represents a substantial fraction of the 
% bioavailable N, and modeling its production and consumption is important to    
% understanding the N cycle processes occurring there, especially those where    
% bioavailable N is lost from or retained within the water column. Here we       
% present the expansion of a global 3D inverse N cycle model to include NO2- as a
% reactive intermediate as well as the processes that produce and consume NO2- in
% marine ODZs. NO2- accumulation in ODZs is accurately represented by the model  
% involving NO3- reduction, NO2- reduction, NO2- oxidation, and anammox. We model
% both 14N and 15N and use a compilation of oceanographic measurements of NO3-   
% and NO2- concentrations and isotopes to place a better constraint on the N     
% cycle processes occurring. The model is optimized using a range of isotope     
% effects for denitrification and NO2- oxidation, and we find that the larger    
% (more negative) inverse isotope effects for NO2- oxidation along with          
% relatively high rates of NO2- oxidation give a better simulation of NO3- and   
% NO2- concentrations and isotopes in marine ODZs.                               
%                                                                                
% How to cite: Martin, T. S., Primeau, F., and Casciotti, K. L.: Modeling        
% oceanic nitrite concentrations and isotopes using a 3D inverse N cycle model,  
% Biogeosciences Discuss., https://doi.org/10.5194/bg-2018-397, in review, 2018. 
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